Malignant hyperthermia is caused by:

 # Malignant hyperthermia is caused by:

A. Suxamethonium

B. Thiopentone

C. Propofol

D. Cis-atracurium

The correct answer is A. Suxamethonium.

Malignant hyperthermia (MH) is a rare but life-threatening condition triggered in susceptible individuals by certain anesthetic agents. Suxamethonium (succinylcholine), a depolarizing neuromuscular blocker, and volatile anesthetic agents (e.g., halothane, sevoflurane) are common triggers. MH is caused by a genetic mutation in the ryanodine receptor (RYR1) or calcium channel, leading to uncontrolled calcium release in skeletal muscle, resulting in hypermetabolism, muscle rigidity, hyperthermia, and rhabdomyolysis.

The other options are not known to cause malignant hyperthermia:

• Thiopentone: A barbiturate used for induction of anesthesia, not a trigger for MH.
• Propofol: An intravenous anesthetic, considered safe in MH-susceptible individuals.
• Cis-atracurium: A non-depolarizing neuromuscular blocker, not associated with MH.